Container base



FIG. 1 is a front perspective view, from above, of the claimed design;

FIG. 2 is a top plan view of the claimed design;

FIG. 3 is an underneath plan view of the claimed design; and,

FIG. 4 is a side view of the claimed design, the opposite side is a mirror image.

The shading on the rim of the container base represents a color contrast with the other portions of the container base, the shape and contour of which do not form a part of the design. 

CLAIM The ornamental design for a container base, as shown and described. 